Why do you need a $500 laptop to talk to basic running on a microcontroller? You realise that old school BASIC can run entirely on the chip itself and thus you only need something that can run a serial terminal right? If you wanted to go crazy you could put a small LCD and a keyboard port on a little micro controller board. Maybe you could get the advanced kids to do that. They might even learn something!
"they can also learn a bit of Linux admin"
Ah, so you're one of the "I have no idea but let's teach it!" crew.
"BASIC? Hang on, while I fetch the DeLorean. 88MPH. GOTO 1985."
BASIC is perfectly fine for kids to pick up the notion that computers take commands and generally run them in order but sometimes there are branches and iteration. What better way to learn branching than to make them make their little LEDs do something different depending on if a button is pressed or not. The reason you sort of people don't understand that is because you have no idea what you actually want kids to learn.